FKBP5 and post-traumatic stress disorder: Studies of stress-related epigenetic changes support this hypothesis that early adversity alters the expression of stress hormone factors implicated in the development of stress-related psychopathology.21,22,23 For example, Klengel and colleagues6,24 showed that childhood trauma-dependent demethylation of a glucocorticoid response element (FKBP5 [OMIM 602623] codes for a nuclear receptor involved in terminating the stress response to threat) resulted in increased risk for the development of posttraumatic stress disorder in adulthood.